In the processing of such silicon wafers, the carriers are exposed to the same identical baths into which the wafers must be immersed. These baths include various corrosive chemicals and certain of the baths are extremely hot, in the range of 180.degree. C. Accordingly, the carriers used to hold the silicon wafers during processing are formed of plastic which is essentially inert and highly resistant to the corrosive effect of the chemicals used, and highly resistive to the high bath temperatures regularly employed during the processing. Conventionally, the molded plastic used in carriers is PFA Teflon, a perfluoroalkoxy-substituted polytetrafluoroethylene resin.
It should be recognized that the silicon wafers are extremely delicate and brittle and may be only a few thousandths of an inch thick. The diameter of such wafers may be in the range of four inches or more. The silicon wafers are extremely valuable, and breakage of a wafer may represent a significant loss.
One of the numerous problems that has been encountered in handling these large but thin silicon wafers is that the wafer baskets which have been known soften when exposed to the 180.degree.-200.degree. C. temperatures, and warping of the carriers also occurs. The warping and bowing or the carriers tends to put added compressive pressure on the edges of the delicate wafers. Breakage has been prevalent due to the forces applied by the carrier and by the warping of the carrier out of its desired and normal rectangular shape. The application of pressure onto the edges of the wafers by the carrier tends to amount to clamping of the wafers in the carrier, making removal of the wafers from the carrier both difficult and hazardous from the standpoint of possible breakage.
Other problems that have existed with previous carriers have related to the inadequate capability of the carrier to allow liquid to pass through the carrier and over the surfaces of the wafers carried thereby. In addition, breakage problems have been encountered during the removal of the wafers from the carrier, while the wafers roll toward the open top after the carrier has been tipped to an inclined position.